Question

In rhombus ABCD, A = 70°. Find CDB.
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Answer 1

Answer:110

Step-by-step explanation:

Sum of all angles in rhombus =180

A =70

Cdb=180-70=110

Answer 2

Step-by-step explanation:

Given that ABCD is a rhombus and DAB = 70°

Since, ABCD is a rhombus so

∠ ABC = ∠ CDA

and ∠ DCB = ∠ DAB = 70° .............(1)

And we know that,

∠ DAB + ∠ ABC + ∠ DCB +∠ CDA = 360°

⇒ 70° + ∠ ABC + 70° + ∠ CDA = 360°

∠ ABC + ∠ CDA + 140° = 360°

∠ ABC + ∠ CDA = 360° - 140°

∠ ABC + ∠ CDA = 220°

Since, ∠ ABC = ∠ CDA 

So, ∠ ABC + ∠ ABC = 220°

2∠ ABC = 220°

∠ ABC = 110°

Thus,

∠ CDB = 1/2(∠ ABC)

= 1/2(110°)

∠ CDB = 55°